Electric control system



y 1939- J. D. RYDER 2,159,181

ELECTRIC common SYSTEM Filed April 19, 1933 2 Sheets-Sheet 1 FIG. I INVENTOR John D. Rqder ATT NEY May 23, 1939.

J. D. RYDER 2,159,181

ELECTRIC CONTROL SYSTEM Filed April 19, 1933 2 Sheets-Sheet 2 INVENTOR Joh n D. Rqder Patented May 23, 1939 UNITED STATES ELECTRIC CONTROL SYSTEM John D. Ryder, Cleveland, Ohio, asaignor to Bailey Meter Company, a corporation of Del- Application April 19, 1933, Serial No. 666,851

12 Claims.

My invention relates to improvements in electric control systems and in particular to an improved electrical circuit including a device susceptible to the relative values of variables, or to the relation between the value of a variable and a predetermined value, for indicating and or controlling the value of such variable or variables.

The variable may be in the nature of a quantity', condition, relation, etc., such, for example,

as pressure, temperature, flow, speed, or any physical, chemical, thermal, electrical, hydraulic or other variable or relation of variables.

In my improved electric circuit, I have primarily a plurality of loop circuits, in one or more 15 of which will be a varying current, electromotive force, or resistance, varying with the value of a variable. A third loop circuit comprises a portion .of each of the said plurality of loops and also a sensitive device, such as a standard galvanometer,

susceptible to differences in voltage drops across the portion of each of the plurality of. loops which is included in the third or galvanometer loop. Now the circuit comprising a galvanometer susceptible to difference in voltage drops might be applied to anything which would cause a change in voltage, current and/or resistance, such, for example, as thermocouples, variable resistances, photo-voltaic cells, etc.

I have, then, a sensitive device, such as the galvanometer, susceptible to differences in voltage drops, where each voltage drop is representative of the value of a variable. The galvanometer is desirably arranged to depart from a predetermined position upon an unbalance in voltage drops, and such departure of the galvanometer needle may initiate an action which may be I utilized to balance the voltage drops and bring the galvanometer needle back to its predetermined balanced position; as well as simultaneously to effect a recording or indication of one or more of the variables and simultaneously control that which will change the value of one or more of the variables.

In the drawings:

Fig. 1 represents in diagrammatic fashion, one

embodiment of my invention utilizing photovoltaic cells and indicating the value of a variable.

Fig. 2 illustrates in diagrammatic fashion, an embodiment similar to Fig. 1. but additionally controlling to maintain substantially uniform the value of the variable being measured.

Fig. 3 represents diagrammatically a further embodiment of the invention utilizing thermoelectric devices such as thermocouples.

5 Fig. 4 represents somewhat diagrammatically another embodiment of the invention for comparing voltage drops eiiected by means of variable resistances.

Referring first to Fig. 1, I show at I a duct such as the uptake duct from a furnace, through 5 which smoke or the gaseous products of combustion continually pass, and having glass or other transparent windows 2, on opposite sides of the duct and in line for the passage of light rays from a source 3. Such light rays are concentrated upon 19 a photo-voltaic cell, such as the commercially known Weston Photronic Cell, indicated at 4, and wherein thelight eifective on the cell will vary primarily with the density of the smoke passing through the duct I The arrangement of a Fig. 1 is primarily for the purpose of indicating and/or recording such smoke density.

A second photo-voltaic cell 5, of similar but not necessarily identical characteristics as the cell 4, also receives light from the source 3. Such 2o photo-voltaic cells are known in the art and, responsive to light, may change their electromotive force, current, and/0r resistance.

I show the cell 5 in a loop circuit including the resistance AB and the cell 4 in a similar loop circuit including the resistance CD. I further show a galvanometer or similar sensitive device G in a third loop circuit including a portion of the resistance AB and a portion of the resistance CD.

In general, the galvanometer G is susceptible 30 to the difference in voltage drops across the portion of each of the two resistances included in its circuit.

In the galvanometer circuit I show a pivoted contact arm S capable of being moved in contact along the resistance CD and a pivoted contact arm I capable of being moved in contact along the resistance AB. The two arms 6, 1 thus provide adjustable means for including in the galvanometer loop a greater or lesser proportion of 40 each of the resistances CD, AB. When light falls upon the cells 4, .5, a current and electromotive force is produced in the respective loop circuits. When calibrated with no smoke passing through the duct I, and the arm I at some point,

for example, B of the resistance AB, then the arm 6 will be at some point E of the resistance CD when the galvanometer G is in neutral or balanced position. The point E of contact for the arm 6 with the resistance CD is determined by 50 moving the arm G.until the galvanometer is in a balanced position, and such calibration takes care of initial differences in characteristics of the cells 4, I, as well as such variations as may exist in the amount of light reaching the cells from the source 3, the amount and resistance of wire in the respective circuits, etc. p

I show the galvanometer needle 8 capable of engaging the contact 9 or it as it moves in one direction or the other from a balanced or neutral position. The needle and contacts are wired to a motor i l, such as a self-starting synchronous motor having opposing fields connected in an alternating current circuit whereby if the needle a. engages the contact 9, one of the fields oi the motor II will be energized for rotation in one direction and if the needle 8 engages the contact it! it will eflect rotation oi the motor ii in the opposite direction. The motor is connected through any suitable known mechanical means, such as gears, indicated by a dotted line I2, with the contact arm I for positioning the same in one direction or the other around its pivot. The motor ii is also connected in suitable manner through proper speed reduction-as indicated at it, with an arm I! comprising a combination indicator and marking pen adapted to be moved relative to an index I5 and a recording chart IS, the latter continuously moved bye.

time means such as a clock 11.

In operation, the system is calibrated by moving the contact arm 6 along the resistance CD to some point E, such that the portion ED of the resistance CD will have a voltage drop equal to that across the resistance AB when the contact This with the light source 3 effective upon the cells 4, 5 and with no smoke passing through the duct; I. The motor II will be in such a position that the contact arm 1 is at B and the indicating arm I4 at zero on the index.

l5 and the recording chart l8. Such, of course, indicates no smoke density through the duct I.

Now when the smoke or gases containing any solid particles pass through the duct I, changing the amount of light reaching the cell .4, then the current and/or electromotive'iorce output of the cell 4 will be varied, thus changing the voltage drop across the res stance ED in a direction to decrease the voltage drop thereacross, and through the unbalance in voltage drops between the resistance portion ED and the resistance AB 'in the galvanometer circuit, the galvanometer needle 8 will swing in one direction until it engages one of the contacts 9, I0, resulting in energization of the motor I i in a direction to position the contact arm I along the resistance AB to decrease the portion included in the galvanometer circuit, until the voltage drop across that portion so included equals or balances that resistance drop through ED and the galvanometer needle, susceptible to the balance or unbalance in voltage drops, will return to its neutral non-contacting position. Such return will stop the motor H and correspondingly the travel of the arm 1. Further change in density of the smoke or gases passing through the duct I will result in an unbalance of voltages between the two portions of resistance included in the galvanometer circuit,

- whereby the needle 8 will swing in one direction or the other, depending upon whether the smoke density has increased or decreased, and correspondingly,-the motor II will be energized for rotation in one direction or the other, moving or positioning the contact arm 1 in proper direction to balance the resistances and voltage drops therethrough and return the galvanometer needle to its neutral or non-contacting position.

Simultaneously with movement of the contact arm I, is eflected a positioning of the indicating arm I! relative to the index it and the chart l8 to provide an indication of smoke density and a continuous record thereof. It will be seen that the less dense the smoke is, the greater amount of light will pass thcrethrough and reach the cell 4, and the closer to the point B will be the contact arm I and the closer to zero will be the indicator arm I relative to the index I5 and the chart IO. Conversely, as the density of the smoke increases, the arm I will move toward the point A and the indicator arm M will move toward maximum reading on the index l5 and on the chart I.

One primary advantage of my invention comprises the arrangement wherein changes in light,

intensity of the source 3, due to changes in voltage, currenhaging, or dust and dirt accumulation on the source, is ineflective or minimized as to eflect upon the accuracy of the indication and recording of smoke density. The same light duct 1.

In Fig. 2, I show a somewhat similar arrangement, except that herein I additionally control the value 01' the density through which the light from the source 3 passes to the cell 4, upon departure of such density from a predetermined value, and to maintain such value. I illustrate at 18 a conduit through which may be flowing, for example, a dye solution in the direction of the arrow. The conduit has at I! glass or other transparent windows through which light from the source 3 may pass to the cell I. Obviously the amount of light passing to the cell 4 will depend upon the density or'light transmitting-properties of the fluid flowing past the windows II. I show at 20 a pipe joining the conduit ll and through which dye or similar material may be red to the fluid under observation to vary the density or color thereof and such addition is controlled through the positioning of a valve 21 in the pipe 2|.

Such cells as the photo-voltaic cells 4, 5 are sensitive to color as well as to light, and the arrangement of Fig. 2 is adapted to work from a comparison of color or wave length of light relative to a standard such as a color screen 22, positioned in the path 0! the light from the source 3 to the cell 5.

Ai'ter initial calibration as described for Fig. 1, the arm 23, adjusted by the turnbuckle 2!, will .be in a position to take care of all discrepancies in the circuit when the color of the fluid passing through the conduit is is the same as the color screen 22. Preferably, when this condition exists, thearm 25 will be at some point near the middle of the resistance AB and the indicator 28 opposite a graduation of the index 15 and the chart l6, denoting similarity between the two colors, namely that of the fluid passing through the conduit l8 and that of the color screen 22, and preferably such line or graduation to be, for example, at the center of the index I5 and the center of the chart graduatlons l8.

Thereafter, upon departure of color of the fluid passing between the windows I9 in one direction or the other from coincidence with the color of the screen 22, the galvanometer needle will depart in one direction or the other and engage either the contact 9 or the contact II for actuating the motor II in proper direction to position the valve 2|, and admit dye. solution at a greater orv lesser rate to the conduit ll for bringing the color of the solution passing therethrough back to the predetermined value.

Simultaneously with the positioning of the valve 2| the motor causes a positioning of the indicator arm 26 and ofthe contact arm 23 to balance the galvanometer circuit. The arrangement being such that the color of the fluid passing the windows I9 is continuously controlled to be in coincidence with the color or the color screen 22. The index l5 and chart li may be calibrated in desirable units of valve position,

'-wave length coIor, or in percentage departure from predetermined coincidence, etc.

I show further in the arrangement, means sensitive to a variable of the flowing fluid for continuously and automatically adjusting the position 01' the arm 23relative to the resistance CD. Such means I have illustrated as a gas-. filled-thermometer system comprising a bulb 21, connected by the capillary 28 with a Bourdon tube 23, whose free end is adapted to position the contact arm 23 along the resistance CD upon change in temperature of the flowing fluid effective upon the bulb 21. I contemplate by this arrangement 'a compensation to the addition of coloring matter through the pipe 20 such as maybe necessary for changes in temperature of the fluid to which the coloring matter is added,

when such changes in temperature may result in different color properties or color absorption properties of the fluid. Broadly I indicate that any variable that would affect the primary control of the light passing quality of the fluid between the windows |9, may be efiective to position the compensating arm 23.

The circuit described, wherein the galvanometer is susceptible to difierence in voltage drops, may be applied in other arrangement wherein variables will cause a change in voltages, current, and/or resistances, such for example, as thermocouples in place of the photo-voltaic cells, previously described. I show in Fig. 3 an arrangement for comparing two temperatures to which thermocouples 30 and 3| are respectively sensitive and specifi cally for indicating and/or recording the departure of the temperature to which the thermocouple 38 is sensitive from the-temperature to which the thermocouple 3| issensitive. The circuit arrangement is similar to that of Figs. 1 and 2 and the galvanometer G is susceptible to the difference in voltage drops-between the portion of the resistances of the thermocouple circuit included in the galvanometer circuit. Upon initial calibration, the arm 6 is positioned along the resistance CD to some point E, and the arm I along the resistance AB so that, regardless of the specific or absolute temperature of the thermocouples 30, 3|, the galvanometer is in balance and its arm 8 at a neutral noncontacting position when the temperature at the thermocouples 30, 3| are the same. Now upon departure of the temperature at the thermocouple 30 from a value the same as that to which the thermocouple 3| is sensitive, in either direction, the difference in voltage drop between the portions of the resistances AB and CD included in the galvanometer circuit will cause the galvanometer to be unbalanced and the arm 8 to engage either the -contact 9 or the contact ID. This will, as previously described, cause the motor I I to be rotated in one direction or the other and through the necessary gears or linkage I2, I3, will position the contact arm I along the resistanceABin adimctionandamount toagainbalance the galvanometer circuit, and simultaneously, the indicator arm I relative to the index II and chart I, to show departure of the temperature to which the thermocouple 38 is sensitive, in

either direction from coincidence with the temperature to which the thermocouple 3| is sensitive.

, Should, however, the temperature at both 38 or 3| increase or decrease together and in the same amount, there will be no unbalance of the galvanometer circuit and no change in position of the contact arm I or the indicator arm M. The indicator arm I will continue to show, relative to th index l5 and the chart I3, that the two temperatures are the same and in coincidence. The indicator will depart from such showing only when the temperature so measured departs from coincidence. I! the index I5 and chart I6 are calibrated in degrees temperature, then the 'arrangement may be such that the armll will continuously indicate actual temperature to which the thermocouple 38 is sensitive so long as the temperature to which the thermocouple 3| remains constant.

. In Fig. 4 I show an arrangement wherein current and/or voltage is supplied to the two loop circuits by batteries 32, 33, respectively, and the value of the current and/or voltage in the respective circuits is varied through the positioning of contact arms 34, 35 along slide wire resistances 36, 31, respectively. The arrangement in general provides a means for comparing variables such as speeds of rotation and the controlling of one such speed to keep it in synchronism with the other, regardless of the absolute value of the speed or speeds.

I show at 38 a steam turbine to which steam is fed through a conduit 33 and whose rate of steam supply is adjusted through the positioning of a valve 40 in the conduit 39. The turbine is provided with a fly-ball. governor 4| arranged so that upon variation in speed and as the fly-balls travel at a greater or lesser radius, the contact arm 35 will be positioned vertically upward or downward relative to the slide wire resistance 31. The position of the arm 35 will thenbe an indication of speed of the turbine 38. t

The arm 34 is adapted to be positioned vertically relative to the slide wire resistance 36, by a similar arrangement of fly-ball governor 42 which is responsive to the speed of a turbine or other rotating machine with which the speed of the turbine 38 is to be kept in synchronism. It is immaterial what the absolute value of speeds are or as to whether the speeds of the two machines are the same or not, but the arrangement contemplates only that the two speeds be kept in synchronism or proportional the one to the other. After initial calibration wherein the arm 6 is moved along the resistance CD to some point E and the galvanometer is in neutral or non-contacting position when the speed of the two machines is in desired proportionality, the indicator arm 26 will be at some designated point on the index l5 and relative to the chart I6, denoting coincidence or desired proportionality between the speeds.

Now upon departure in speed of the machine 38 from that whose speed is represented by the fly-ball governor 42, the voltage drops will become unbalanced and the galvanometer needle 8 depart in one direction or the other from a noncontacting position and engage either the contact 8 or the contact III. This, as previously deiii) 1 or other effects in portions or" the scribed, causes an energization of the motor II to position the arm I and the indicator arm 2i by means of proper gearing H and simultaneously through gearing 43, will position the control valve 40 to bring the speed of the machine 38 into synchronism.

It will be seen that while I have described certain preferred arrangements and embodiments of my invention, I am not to be limited thereby except as to the claims in view of prior art. The arrangement comprises in general a galvanometer or other sensitive device of similar nature, susceptible to voltage drops between two portions of the circuit in which the galvanometer is included. The voltage drop through each of these portions may be representative of the value of a variable, such as temperature, pressure, speed, quantity, rate of fiow, etc., and may be accomplished by variation in current, potential and/or in resistance.

While I have illustrated various means and Ways of changing the voltage drop across the portions of the resistances included in the galvanometer circuit, it is not necessary that 1 ice restricted merely to those which I have shown to illustrate and describe. I contemplate broadly that the galvanometer is susceptible to a difference between voltage drops which may be caused in any desired manner and representative of the value or relation of variables which may be of a physical, chemical, electrical, hydraulic, or other nature, or may be varied by hand or by the positioning of any object.

I may utilize the comparison of voltage drops galvanome r circuit to record departure iron: unity or other proportional relations between the said voltage drops or in absolute value, or may utilize such departure or value in re-balancing the galvanonieter circuit or in the control one or more of the variables.

llVhat I claim as new and desire to secure Letters Patent e United States, is:

i. in combin a pair of similar electric circuits, a pal errnocouples sensitive to varying temperature conditions and connected one each circuit, a resistance in each circuit, third circuit includi g a variable portion of each o said resistances, a galvanometer in said thir circuit susceptible to the differential in volta drops across the portion of the resistances in its circuit, and means under the control oi aid salvanorneter adapted to re-balance said voltage drops after a departure from balance.

2. in combination, a pair of similar electric circuits, a pair of thermocouples sensitive to varying temperature conditions and connected one in each circuit, a resistance in each circuit, a third circuit including a variable portion of each or" smd resistances,- a galvanometer in said third circuit susceptible to the cliflerential in voltage drops across the portion of the resistances in its circuit, means under the control of said galvanorneter adapted to re-balance said voltage drops after a departure from balance, and means positioned with said last-named means for advising the instantaneous difference between the temperature conditions to which the thermocouples are sensitive.

3. In combination, a first electric circuit including a resistance, a second electric circuit including a resistance, a third electric circuit including a galvanometer and a variable portion of each or" said resistances, means under the control of a variable for varying in step therewith the voltage drop through the resistance of the first electric circuit, means under the control of a variable to be compared to the first variable for varying in step therewith the voltage drop through the resistance of the second electric circuit, the galvanometer susceptible to the differentlal in voltage drops across said portions whereby the galvanometer is in balance when the value of said two variables is in desired proportionality, and means under the control of said galvanometer when it departs from balance for varying the portion of the second resistance which is included in the galvanometer circuit.

4. A galvanometer circuit including in combination, a galvanometer and a plurality of variable resistances, said galvanometer sensitive to unbalance oi voltage drops across said resistances, means for causing a voltage drop across one of the resistances representative of the value of a variable, means for causing a voltage drop across another of the resistances representative of the value of a second variable whose instantaneous value is to be compared to that of the first variable, and means under the control of said galvanorneter for rte-balancing the galvanometer after it has been unbalanced by a departure of said variables from desired proportionality.

5. In combination, pair of separate electric circuits each including a photo-voltaic cell and a resistance, means for varying the currents procluced by said cells, a circuit associated with said first-named circuits including a galvanometer arranged. compare voltage dropsl through portlons oi resistances, means under the control of said galvanometer for varying one of portions to maintain said voltage drops combination, a oi. se Jarate electric circuits ea ncluding a photo-voltaic cell and a slide wire re nee, means for varying the currents prorluc by said cells, a movable contact an -l engaging each of slide wire resistances, a circuit associated with said first-named cir cuits said contact arms and including a gal vanonieter arranged to compare the voltage d pa across portions said resistances determined by the position of said contact arms, and means under the control of said galvanometer for moving one of said contact arms along its associated slide wire.

'7. In combination, a pair of separate electric circuits each including a resistance and means for producing a variable voltage drop across the resistances, a movable contact arm engaging each of we resistances, a galvanometer, a connection between said galvanometer and each of said contact arms, the galvanometer arranged to compare voltage drops across portions of said resistances determined by the position of said contact arms, and means under the control of said galvanorneter for moving one of said contact arms along its associated resistance, to maintain said voltage drops equal.

8. in combination, a pair of similar electric circuits, a photo-voltaic cell in each circuit, a resistance in each circuit, a light source effective upon both cells, a fluid of varying light obstructing density in the light path to one of the cells, a third circuit including a variable portion of each of said resistances, a galvanometer in said third circuit susceptible to the differential in voltage drops across the portion of the resistances in its circuit, a sell-starting motor having opposed fields,'means controlled by said galvanometer ior selectively energizing one or the other oi said flelds in accordance with variations in fluid density, and an o ive connection between said motor and one or said resistances for varying the voltage-drop of one of the resistances effective upon the galvanometer to balance same after displacement from balance due to variations in fluid density.

9. In a fluid density indicator and/or recorder,

a pair of similar electric circuits each including a fields for varying the portion of one 0! said 11csistances in circuit with said galvanometer.

10. In combination, a pair of separate electric circuits, each including a resistance and means for producing a variable voltage drop across the resistances, a contact arm engaging each of said resistances, a reversible motortor operating one of said contact arms, a galvanometer sensitive to the voltage drop across portions of said resistances determined by the positions of said contact arms, and contact means actuated by said galvanometer for controlling said motor to maintain said voltage drops equal.

11. In combination, an electric circuit comprising a slide wire resistance and a photovoltaic cell, a second circuit comprising a slide wire resistance and a photo-voltaic cell, a source of light for energizing said cells, a fluid oi varying light obstructing density in the light path to one oi the cells, a movable contact arm engaging each of said slide wire resistances, means for determining the diflerence in voltage drops through portions oi said resistances determined by the positions of said contact arms relative to their associated slidewires comprising a galvanometer having a movable member adapted to deflect from a neutral position in accordance with changes in said difference from a predetermined value, a reversible motor having opposed flelds for moving the contact arm associated with the slide wire resistance in said second named circuit, and contact means actuated by said movable member when deflected from a neutral position to control said motor to maintain said diiierence at the predetermined value.

12. In combination, a pair of separate electric circuits each including a photo-voltaic cell and a resistance, light means for varying the currents produced by said cells, a circuit associated with said first-named circuits including a galvanometer arranged to compare voltage drops through portions oi said resistances, and means under the control oi! said galvanometer tor varying one of said portions.

JOHN D. RYDER. 

